Technical Field of the Invention
The invention relates to the use of a quantitative functional MRI (fMRI), mapping technique to discern human responses to olfactive stimuli in particular stimuli by fragrance ingredients, accords or fully formulated fragrances which induce a reward effect.
Background Art
Traditional consumer research techniques have only limited success in predicting whether a product will be a commercial success or not. It is desirable to have a technique of measuring brain response to stimuli without the time and reflection required in formulating and expressing ideas verbally, in response to questions. Magnetic resonance imaging techniques offer a way of investigating how a consumer responds to a stimulus in a non verbal way while the brain interprets the stimulus; it allows visualization of both primary response (e.g. in the piriform cortex, PC) and further processing of the sensory signals (e.g. in the orbitofrontal cortex, OFC). The consumer has to use, or experience the product in order to react to it and in the context of measuring brain response by MRI this may be difficult for many products. However it is possible to introduce olfactive stimuli to subjects in an accurate and precise way, whilst measuring brain response, using a specific form of olfactometer.
An olfactometer is a device designed to provide a number of olfactive stimuli to subjects in a controlled and reproducible way. The requirements of the MRI scanning technique impose restrictions on the design of olfactometers suitable for use in conjunction with MRI scanners. One major restriction is the elimination of magnetic materials from within the vicinity of the scanner. Due to the availability of olfactometers which can be used in conjunction with MRI scanners the interest in measuring brain response by MRI to olfactive stimuli has increased significantly in the past few years. Most of the interest in MRI measurement with olfaction has centered on hedonic responses to stimuli (see for example Zatorre R. L. Jones-Gottman M, Rouby C, Neural mechanisms involved in odor pleasantness and intensity judgements Neuroreport 11 2711-2716 (2000) or Kobal G, Kettenmann B, Int. J. Psychophysiology 36 (2) 157-163 2000).
A widely held view on emotional response is that we have 6 basic emotions (Ekman et al, J of Personality and Social Psychology 1987 v53, p 712):                Anger        Disgust        Fear        Happiness        Sadness        Surprise.        
These emotions are related to reward, but reward is an effect of activating these emotions; in fact, an outcome of activation of all of these emotions may be reward (if you overcome fear than you are brave and will be rewarded; next time maybe you will be seeking fear to experience this reward etc.).
The dopaminergic pathway is sometimes called the reward pathway, and is generally associated with functions such as:                motivation and emotional response        reward and desire        pleasure, euphoria        addiction, compulsion.        
Rewards are generally experienced as “making things better” and are thus liked, desired, and pursued. Reward may be expressed using words or expressions that communicate an intense feeling of well-being.
The areas of the brain involved in the dopaminergic pathway are well understood, and general descriptions can be found in a standard text such as The Brain Atlas, T. A. Woolset et al (Wiley 2008, ISBN 978-0-470-08476-2), with more specific details in review articles such as “Dopaminergic reward system: a short integrative review” by O. Arrias-Carrion et al, International Archives of Medicine 2010, 3:24, and in Everitt et al, Brain Res Brain Res Review 36, p 129-138 (2001). The pathway involves the Ventral Tegmental Area (located in the dopaminergic Midbrain), Nucleus Accumbens, Striatum (Caudate Nucleus and Putamen), Amygdala, Hippocampus and Prefrontal Cortex (Superior, Middle, Inferior frontal gyrus) and Anterior Cingulate gyrus.
In a review of fMRI studies using diverse stimuli, Sharpley and Bitsika (Behav Brain Res 2010 Jul. 13) note that the Ventral Tegmental Area (VTA) was activated by both maternal and romantic love, and commented that in almost all studies of love, humour and other forms of pleasure, the areas activated are also those associated with reward processes. Sharpley et al. also noted that activation of the VTA and Nucleus Accumbens was also associated with Joy/Happiness/Laughter, and this can be understood in the context that they are often the rewarding outcomes of an emotional experience.